The long range goal is to examine the development of the vertebrate central nervous system with sufficiently sensitive biochemical and cell biological techniques that conclusions can be drawn concerning the sequence of potential morphogenetic interactions of individual neurons. The scope of this research plan is restricted to the visual system of lower vertebrates with particular emphasis on the patterning of axonal terminals of retinal ganglion cells within the brain. Intraocular, focal or intracellular injection with isotopes that label optic terminals is combined with high resolution autoradiography of selected visual centers to probe the developmental sequence of normal cellular contacts. An additional series of experiments has been designed around an in vitro assay of selective cell adhesions and the specificity of surface glycosyltransferases. Both experimental protocols confront significant questions raised by the techniques of embryology and sensory physiology: the pattern of optic fiber synaptogenesis, the status of neuronal specificity and the interpretation of retinal specification at the cellular level.